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/**
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 *        Name: DBSAXHandler.java
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 *     Purpose: A Class that implements org.xml.sax.EntityResolver interface
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 *              for resolving external entities
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 *   Copyright: 2000 Regents of the University of California and the
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 *              National Center for Ecological Analysis and Synthesis
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 *     Authors: Jivka Bojilova
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 *
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 *     Version: '$Id: DBEntityResolver.java 74 2000-05-05 00:37:58Z jones $'
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 */
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package edu.ucsb.nceas.metacat;
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import org.xml.sax.*;
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import java.sql.*;
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import java.net.URL;
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import java.net.MalformedURLException;
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import java.util.Stack;
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import java.util.EmptyStackException;
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/** 
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 * A database aware Class implementing EntityResolver interface for the SAX parser to
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 * call when processing the XML stream and intercepting any external entities
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 * (including the external DTD subset and external parameter entities, if any) before including them.
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 */
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public class DBEntityResolver implements EntityResolver
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{
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   static String doctype = null;
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   static Connection conn = null;
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   private int pIdCounter = 0;
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   private long currentElementNo;
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   /** Construct an instance of the DBEntityResolver clas
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    *
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    * @param conn the JDBC connection to which information is written
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    */
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   public DBEntityResolver(Connection conn)
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   {
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      this.conn = conn;
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   }
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   /** The Parser call this method before opening any external entity 
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     * except the top-level document entity (including the external DTD subset,
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     * external entities referenced within the DTD, and external entities referenced 
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     * within the document element)*/
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   public InputSource resolveEntity (String publicId, String systemId)
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            throws MalformedURLException
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   {
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     String dbSystemId;
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     if (publicId != null) {
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        pIdCounter += 1;
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        currentElementNo = DBSAXHandler.elementNo;
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        System.out.println("from DBEntityResolver: current element is " + DBSAXHandler.elementNo);
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        System.out.println("from DBEntityResolver: " + pIdCounter + " " + publicId);
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        // look at the db XML Catalog and get dbSystemId by this publicId
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        if (currentElementNo == 0) {
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            doctype = publicId;
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            dbSystemId = getDTDSystemID (conn, publicId);
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            if (dbSystemId == "")
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                // register publicId in db and use the provided systemId
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                if (systemId != "") {
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                    System.out.println("from DBEntityResolver: " + systemId);
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                    new URL(systemId);
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                    registerDTDPublicID (conn, publicId, systemId);
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                    return null;
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                }
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            new URL(dbSystemId);
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            System.out.println("from DBEntityResolver: db System ID: " + dbSystemId);
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            return new InputSource(dbSystemId);
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        } 
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        else {
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            // look at the db XML Catalog and get dbSystemId by this publicId for a given doctype
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            dbSystemId = getEntitySystemID (conn, doctype, publicId);
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            if (dbSystemId == "")
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                // register publicId in db for a given doctype and use the provided systemId
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                if (systemId != "") {
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                    System.out.println("from DBEntityResolver: " + systemId);
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                    new URL(systemId);
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                    registerEntityPublicID (conn, doctype, publicId, systemId);
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                    return null;
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                }
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            new URL(dbSystemId);
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            System.out.println("from DBEntityResolver: db System ID: " + dbSystemId);
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            return new InputSource(dbSystemId);
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        }  
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     }
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     if ( systemId != null) {
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        System.out.println("from DBEntityResolver: " + systemId);
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        new URL(systemId);
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     }
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     // use the default behaviour
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     return null;
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   }
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   /** Look at db XML Catalog to get System ID (if any) for that Public ID.
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     * Return empty string if there are not */
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   private String getDTDSystemID (Connection conn, String publicId)
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   {
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        String system_id = "";
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        Statement stmt;
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        try {
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          stmt = conn.createStatement();
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          stmt.execute("SELECT system_id FROM xml_catalog_entities a, xml_catalog b " + 
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                       "WHERE a.entity_type = 'DTD' AND a.source_doctype = b.doctype AND b.doctype = '" + publicId + "'");
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          try {
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            ResultSet rs = stmt.getResultSet();
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            try {
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              boolean tableHasRows = rs.next();
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              if (tableHasRows) {
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                try {
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                  system_id = rs.getString(1);
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                } catch (SQLException e) {
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                  System.out.println("DBEntityResolver.getDTDSystemID() - Error with getString: " + e.getMessage());
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                }
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              }
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            } catch (SQLException e) {
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              System.out.println("DBEntityResolver.getDTDSystemID() - Error with next: " + e.getMessage());
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            }
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          } catch (SQLException e) {
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            System.out.println("DBEntityResolver.getDTDSystemID() - Error with getrset: " + e.getMessage());
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          }
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          stmt.close();
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        } catch (SQLException e) {
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          System.out.println("DBEntityResolver.getDTDSystemID() - Error getting id: " + e.getMessage());
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        }
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        // return the selected System ID
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        return system_id;
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   }
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   /** Register Public ID in db XML Catalog */
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   private void registerDTDPublicID (Connection conn, String publicId, String systemId)
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   {
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        try {
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          conn.setAutoCommit(false);
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          PreparedStatement pstmt;
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          pstmt = conn.prepareStatement(
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                "INSERT INTO xml_catalog (doctype) VALUES (?)");
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          // Bind the values to the query
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          pstmt.setString(1, publicId);
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          // Do the insertion
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          pstmt.execute();
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          pstmt.close();
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          pstmt = conn.prepareStatement(
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                "INSERT INTO xml_catalog_entities (entity_id, entity_type, source_doctype, system_id) " +
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                "VALUES (null, 'DTD', ?, ?)");
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          // Bind the values to the query
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          pstmt.setString(1, publicId);
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          pstmt.setString(2, systemId);
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          // Do the insertion
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          pstmt.execute();
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          pstmt.close();
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          conn.commit();
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          conn.setAutoCommit(true);
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        } catch (SQLException e) {
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          System.out.println(e.getMessage());
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        }
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   }
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   /** Look at db XML Catalog to get System ID (if any) for that Public ID and doctype.
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     * Return empty string if there are not */
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   private String getEntitySystemID (Connection conn, String doctype, String publicId)
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   {
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        String system_id = "";
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        Statement stmt;
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        try {
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          stmt = conn.createStatement();
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          stmt.execute("SELECT system_id FROM xml_catalog_entities " + 
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                       "WHERE entity_type = 'ENTITY' AND source_doctype = '" + doctype + "' AND public_id = '" + publicId + "'");
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          try {
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            ResultSet rs = stmt.getResultSet();
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            try {
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              boolean tableHasRows = rs.next();
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              if (tableHasRows) {
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                try {
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                  system_id = rs.getString(1);
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                } catch (SQLException e) {
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                  System.out.println("DBEntityResolver.getEntitySystemID() - Error with getString: " + e.getMessage());
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                }
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              }
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            } catch (SQLException e) {
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              System.out.println("DBEntityResolver.getEntitySystemID() - Error with next: " + e.getMessage());
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            }
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          } catch (SQLException e) {
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            System.out.println("DBEntityResolver.getEntitySystemID() - Error with getrset: " + e.getMessage());
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          }
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          stmt.close();
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        } catch (SQLException e) {
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          System.out.println("DBEntityResolver.getEntitySystemID() - Error getting id: " + e.getMessage());
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        }
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        // return the selected System ID number
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        return system_id;
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   }
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   /** Register Public ID in db XML Catalog */
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   private void registerEntityPublicID (Connection conn, String doctype, String publicId, String systemId)
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   {
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        try {
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          conn.setAutoCommit(false);
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          PreparedStatement pstmt;
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          pstmt = conn.prepareStatement(
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                "INSERT INTO xml_catalog_entities (entity_id, entity_name, entity_type, source_doctype, public_id, system_id) " +
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                "VALUES (null, null, 'ENTITY', ?, ?, ?)");
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          // Bind the values to the query
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          pstmt.setString(1, doctype);
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          pstmt.setString(2, publicId);
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          pstmt.setString(3, systemId);
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          // Do the insertion
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          pstmt.execute();
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          pstmt.close();
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          conn.commit();
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          conn.setAutoCommit(true);
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        } catch (SQLException e) {
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          System.out.println(e.getMessage());
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        }
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   }
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}
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